From: LARRY KLAES (ljk4_at_msn.com)
Date: Thu Mar 06 2003 - 23:35:02 PST
----- Original Message -----
From: NASA Jet Propulsion Laboratory
Sent: Thursday, March 06, 2003 10:02 PM
To: ljk4_at_msn.com
Subject: Rising Storms Revise Story of Jupiter's Stripes
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NEWS RELEASE: 2003-031 March 6, 2003
Rising Storms Revise Story of Jupiter's Stripes
Pictures of Jupiter, taken by a NASA spacecraft on its way to Saturn,
are flipping at least one long-standing notion about Jupiter upside
down.
Stripes dominate Jupiter's appearance. Darker "belts" alternate with
lighter "zones." Scientists have long considered the zones, with their
pale clouds, to be areas of upwelling atmosphere, partly because many
clouds on Earth form where air is rising. On the principle of what
goes up must come down, the dark belts have been viewed as areas where
air generally descends.
However, pictures from the Cassini spacecraft show that individual
storm cells of upwelling bright-white clouds, too small to see from
Earth, pop up almost without exception in the dark belts. Earlier
spacecraft had hinted so, but not with the overwhelming evidence
provided by the new images of 43 different storms.
"We have a clear picture emerging that the belts must be the areas of
net-rising atmospheric motion on Jupiter, with the implication that
the net motion in the zones has to be sinking," said Dr. Tony Del
Genio, an atmospheric scientist at NASA's Goddard Institute for Space
Studies, New York. "It's the opposite of expectations for the past 50
years".
Del Genio is one of 24 co-authors from America and Europe reporting
diverse results from the Cassini imaging of Jupiter in Friday's
edition of the journal Science. Cassini's camera took about 26,000
images of Jupiter, its moons and its faint rings over a six-month
period as the spacecraft passed nearby two years ago.
"The range of illumination angles at which Cassini viewed Jupiter's
main ring gives insight about particles in the ring by the way they
scatter sunlight. The particles appear to be irregularly shaped, not
spheres," said camera-team leader Dr. Carolyn Porco of Southwest
Research Institute, Boulder, Colo. "They likely come from surfaces of
one or more moons being eroded by micrometeoroid impacts."
Spherical particles would suggest an origin as melted droplets, not
erosion. In addition, Cassini imaging shows the degree to which the
orbits of two small moons near the ring, Metis and Adrastea, are
inclined matches the vertical thickness of the ring. That points to
those moons as sources of the ring particles, said Porco.
One surprise in ultraviolet images of Jupiter's north polar region is
a swirling dark oval of high-atmosphere haze the size of the planet's
famous Great Red Spot. "It's a phenomenon we haven't seen before, so
it gives us new information about how stratospheric circulation
works," said Dr. Robert West of NASA's Jet Propulsion Laboratory,
Pasadena, Calif. The results show the winds and the life cycle of
clouds in the stratosphere.
Also, movies of infrared images reveal persistent bands of
globe-circling winds extending north of the conspicuous dark and light
stripes. "The planet's appearance at high latitudes is like leopard
spots, but when you see it in motion, it's interesting that all the
spots at one latitude move in one direction and all the spots at
adjacent latitudes move the opposite direction," said Dr. Andrew
Ingersoll of the California Institute of Technology, Pasadena.
Other discoveries reported include atmospheric glows of the large
moons Io and Europa during eclipses, a volcanic plume over Io's north
polar region, and the irregular shape of a small outer moon, Himalia.
"The Jupiter results provide some hints of the spectacular new
findings that await Cassini when it reaches Saturn," Dr. Larry
Esposito of the University of Colorado, Boulder, principal
investigator for Cassini's ultraviolet-imaging spectrograph
instrument, predicts in a separate commentary in Science about the
Cassini camera results at Jupiter. Cassini will begin orbiting Saturn
July 1, 2004, and will release its piggybacked Huygens probe about six
months later for descent through the atmosphere of the moon Titan.
Cassini is a cooperative venture of NASA, the European Space Agency
and the Italian Space Agency. JPL, a division of Caltech, manages the
mission for NASA's Office of Space Science, Washington, D.C. Other
co-authors include scientists from Cornell University, Ithaca, N.Y.;
Free University of Berlin, Germany; Queen Mary, University of London,
United Kingdom; University of Arizona, Tucson; University of Paris,
France; German Aerospace Center, Berlin; and University of California,
Los Angeles.
Images and mission information are available on the Internet at:
http://saturn.jpl.nasa.gov/gallery/jupiter-flyby/index.cfm and
http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html
-end-
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